The overall goal of this program project is to identify and characterize new and alternative mechanistic targets by which estrogens and progestins are neuroprotective. This program of research is driven by a critical need to improve our understanding of steroid hormone neurobiology, a need that became evident following the results of the Women's Health Initiative Memory Study that identified effects of estrogen and/or progestins that were contrary to expectation. To address this need, we have organized a program of research consisting of 4 highly interactive research projects and 2 supportive cores. The studies proposed in these projects challenge the field to consider a novel membrane PR (Project 1), a mitochondria-localized estrogen receptor (Project 2), intracellular Ca2+channels, including IPS receptors and a novel mitochondrial ryanodine receptor (Project 3), and a previously ignored, naturally occurring estrogen, 17a-E2 (Project 4), as critical players in neuroprotection and/or neurogenesis. Supporting these projects will be the Administrative Core (Core A) that not only oversees the program of research, but will also provide biostatistical support and a common animal model (ovariectomized animals that have undergone transient cerebral ischemia) to the projects, the latter serving as a point of integration for the research performed in the individual projects. In addition, the Mass Spectrometry Core (Core B) will serve all 4 projects by providing powerful tools to assess brain steroid levels and for the routine identification and/or quantification of proteins and their posttranslational modifications, which will serve to enhance the Program's ability to define relevant mechanistic targets of estrogens and progestins. Through the successful completion of the proposed research, we expect to have identified key players in the neuroprotection cascade relevant to the protective effects of estrogen and progesterone. In particular, we will have identified the most protective hormone along with their important intracellular targets that are critical for protecting neural tissue, which can in turn, be exploited for the development of safer and more effective therapeutic strategies for treating the menopause and age associated disorders such as Alzheimer's disease, whose incidence and risk increases in the postmenopausal period.